This invention relates to impeller assemblies that are commonly used in pumps for liquids. In particular, this invention relates to the assembly of impeller components.
Impeller assemblies typically include an impeller housing which is mounted on or operably connected with a central drive shaft. Attached to the shaft, within the housing, is an impeller. The impeller typically includes upper and lower cover plates and, in applications where the impeller is manufactured from pressed metal components, a vane plate located between the respective cover plates. Alternatively, the vanes of the impeller may be formed integrally with one or both cover plates. Fluid to be pumped is introduced into the impeller housing at one side thereof. The shaft rotates so as to rotate the impeller assembly thereby creating regions of high and low fluid pressure within the impeller housing and impelling fluid through the assembly.
Depending on the application of the pump, a pump can be a single-stage model i.e. having one impeller assembly, or a multi-stage model i.e. having a number of impeller assemblies in series on the same shaft passing through each of the impeller housings.
Typically, the lower cover plate of the impeller assembly incudes a central boss, formed integrally with the cover plate. The central boss defines an aperture and receives the drive shaft of the impeller assembly. The boss is typically keyed to the drive shaft so that the drive shaft directly drives the lower cover plate. The vane plate and upper cover plate have central apertures, considerably larger than the drive shaft and are located over the boss of the lower plate. The vane plate and upper cover plate are fastened to the lower cover plate e.g by welding at the vanes, gluing, or riveting. As such, the load of the entire impeller is carried by the lower cover plate as it is rotated by the drive shaft.
This distribution of load can lead to several problems when the impeller is in operation, particularly during acceleration/deceleration which may be experienced during start up or engine braking or may be due to the introduction of a foreign object into the pump housing. Because the lower cover plate only is being driven, the inertial loads of the entire impeller are transmitted to the drive feature of the lower cover plate. This plate must be accordingly stronger to resist these loads, which typically leads to a heavier, more expensive, drive feature requirement.
In the case of a laminated, pressed metal impeller, the lower plate is typically manufactured from thicker gauge material to compensate for the extra loading. In a diecast impeller, extra thickness is added locally around the drive.
Manufacture of an impeller assembly in this manner is time consuming and labour intensive, requiring, in the case of welding, numerous spot welds between the lower cover plate and the vane plate, and between the vane plate and the upper cover plate. The plates must be securely fixed together so as to prevent slippage and fluid flow between the plates.
In the case of plastic impellers, welding can introduce variation in the axial length of the impeller assembly. With too much welding, this length is reduced, leading to a reduction in the impeller flow output. With insufficient welding, the impeller axial length will be increased, potentially leading to overloading of the drive motor.
Mechanical fastening, in the form of riveting can lead to failure due to fretting and is also known to lead to corrosion problems, as materials are more prone to stress induced corrosion after riveting.
Permanent fastening of the impeller components also prevents easy dismantling and replacement of individual components in the assembly if they become worn or faulty.
The above disadvantages are of course amplified when the pump is a multi-stage model. In particular, variation in the axial length of individual assemblies is multiplied, leading to fitment problems on mating seal components, in addition to the performance variation described previously.
It is therefore an object of the invention to provide an impeller assembly that at least in part alleviates one or more of the above disadvantages.
The invention accordingly provides an impeller assembly including:
an impeller, the impeller including:
wherein the impeller assembly further includes means for applying force parallel to the axis of the impeller to the impeller so as to clamp the pair of plate means and intermediate vane means together.
Advantageously, the pair of plate means define upper and lower cover plates of the impeller. Each of the upper and lower cover plates and the vane means preferably include a central aperture adapted to receive the drive shaft. The respective central apertures are preferably keyed to the shaft such that each impeller component is separately driven by the drive shaft. The central apertures, and a corresponding portion of the exterior surface of the drive shaft, may be formed with pair of opposed flats, or may be octagonal or hexagonal, for example.
Advantageously, the vane means define fluid flow paths and are located intermediate the upper and lower cover plates. One or both of the pair of plate means may incorporate the vane means. Preferably, the vane means are formed integrally with the lower cover plate. Alternatively, the vane means may be a separate vane plate which is disposed between the upper and lower cover plates.
Preferably, the drive shaft includes a portion larger in diameter than the keyed portion of the shaft thereby defining a step. When the impeller is assembled, the lower cover plate advantageously sits adjacent and is pressed against the step of the shaft.
The impeller assembly preferably further includes a generally cylindrical spacer means. One end of the spacer means if preferably received within a central portion of the upper cover plate. The end of the spacer not received by the upper cover plate serves as a support for either the lower cover plate of the next impeller in series in multi-stage model pumps, or for the tightening nut, depending on the location of the impeller within the pump.
In one embodiment of the invention, the means for applying force to the impeller is preferably a combination of the stepped shaft, a tightening nut, and one or both of the pair of plate means.
In this embodiment, the outside annular portion of the upper cover plate surrounding the central aperture, is tapered downwardly and outwardly from the central aperture. When force is applied to the upper cover plate by the tightening nut, the tapered portion is forced downwardly and caused to deform outwardly against the adjacent lower cover plate or vane means.
The outside annular portion of the lower cover plate surrounding the central aperture may also be tapered, in this case, upwardly and outwardly from the central aperture. When force is applied to the lower cover plate by the tightening nut, the tapered portion of the lower cover plate is forced upwardly and caused to deform outwardly against the adjacent upper cover plate or vane means.
Deformation of either or both of the upper and lower cover plates assists in maintaining pressure and therefore a seal between the impeller components.
One end of the drive shaft preferably includes a screw thread or similar corresponding to a screw thread on the tightening nut. The tightening nut is fitted to the drive shaft and as it is tightened, respective spacers and impeller plates in the impeller assembly are clamped against the stepped portion at the opposite end of the drive shaft.
The invention also extends to a pump for liquids, the pump including an impeller housing having an inlet port and an outlet port, and at least one impeller assembly, according to an embodiment of the invention, located between the inlet port and the outlet port and operable to impel liquid from the inlet port to the outlet port.
Preferably, the pump includes a plurality of impeller assemblies arranged in series between the inlet port and outlet port.
The invention will now be described by way of example, with reference to the accompanying drawings, in which:
Referring to the drawings,
Vane plate 15 may be constructed in any conventional manner. The vanes of vane plate 15 may be formed integrally on the interior face of the lower cover plate such that they are intermediate the lower and upper cover plates. The vanes extend between the upper and lower plates so as to form passageways for fluid from the centre of the impeller to the outer edge of the impeller. The vanes are typically involute and serve to create regions of high and low pressure within the impeller assembly, as it is rotated at high speed, so as to impel fluid through the assembly.
Vane plate 15 is typically of pressed metal construction, however in this design it may instead be manufactured from a relatively soft polymeric material so as to improve sealing between the impeller components.
As shown in
The arrows in
A collar spacer 16 is provided and serves the dual purpose of spacing adjacent impeller assemblies in series in multi-stage pumps, and as a means for nut 32 to act on, as described below. Spacer 16 is generally cylindrical and has an upper end 18 and lower end 17. Lower end 17 is received within the central portion 21 of upper cover plate 12. Drive shaft 28 extends coaxially through the hollow interior 13 of collar spacer 16.
In one embodiment of the invention, the lower end 17 of spacer 16, may be formed as a broadly flared or frustoconical portion 19. The flared or frustoconical portion 19 extends radially from the lower end 17 to an annular end face 20, as best illustrated in FIG. 3. In this embodiment, the flared or frustoconical portion 19 acts as a diaphragm, eliminating freeplay between individual components. When a force is applied to the upper end 18 of the collar spacer 16, the frustoconical portion 19 is forced downwardly and is caused to deform outwardly against the facing surface of the upper cover plate, generating an opposing axial load. This loading assists in maintaining the pressure applied to the impeller components thereby maintaining them in a substantially fluid tight relationship and also acts as a brake on the locking nut 32, preventing accidental disengagement.
As described above, shaft 28 is keyed to receive the impeller plates. This keyed region is indicated at “A” in FIG. 3. One end 29 of the shaft 28 is not keyed and has a larger diameter than portion “A” so as to create an annular step 30. Lower cover plate 14 of the impeller assembly sits against step 30 when the impeller plates are located on the drive shaft 28. The opposite end 31 of the shaft 28 is provided with a screw thread or similar to receive nut 32.
To assemble the impeller assembly, the lower cover plate 14, vane plate 15, and upper cover plate 12, are placed on the shaft 28 in sequence, such that lower cover plate 14 sits against step 30. Spacer 16 is then placed on the shaft such that lower end 17 is received by upper cover plate 12. If the pump is a multi-stage model, successive impeller assemblies are mounted on the shaft, such that a spacer 16 is always placed on the shaft last. Nut 32 is then tightened onto the shaft against the upper end 18 of the exposed spacer 16 thereby pressing spacer 16 and subsequent spacers against step 30. As a result, the impeller plates are tightly pressed together thereby forming an assembly of impellers. When it is necessary to remove or replace one or more of the impeller plates, the nut 32 is removed and the impeller plates removed and replaced as required.
An impeller assembly according to a second embodiment of the invention is illustrated in
Referring to
As shown in
Upper cover plate 112 also includes a central aperture 122. The interior walls 43 of the central aperture 122 define a hexagon which corresponds to the exterior surface of the drive shaft as for the lower cover plate 114. Spaced radially from the central aperture is an annular flange 44 extending coaxially with the drive shaft. The annular region 45 between the annular flange 44 and the central aperture 122 is spanned by a plurality of support members 46 which connect the annular flange 44 to the central aperture 122. The annular region 45 is left substantially open to allow fluid flow into the impeller assembly 110. The support members 46, are preferably formed as additional impeller blades, thereby increasing the efficiency of the impeller.
As best illustrated in
In multi-stage model pumps, subsequent impeller assemblies are located on the drive shaft in series. These multiple impeller assemblies are separated by a collar spacer (not shown). The collar spacer is generally cylindrical tube. The collar spacer is located on the drive shaft between adjacent upper and lower cover plates in series and serves the dual purpose of spacing adjacent impeller assemblies in series in multi-stage pumps, and as a means for a nut (32 as shown in
The tapered outside portion 125 of the upper cover plate 112 acts as a diaphragm in the same manner as the flared or frustoconical portion 19 of the first embodiment of the invention. When a force is applied to the upper annular face 47 of the central portion 121, (either by the spacer or nut 32 depending on where the impeller assembly is located in the stack), the tapered portion 125 is forced downwardly and is caused to deform outwardly against the vanes 115 on the lower cover plate 114. This loading assists in maintaining the pressure applied between the impeller components and eliminates freeplay between individual components.
In a third embodiment of the invention, illustrated in
As in previous embodiments, upper and lower cover plates 212, 214 also include central portions 221 and central apertures 222, and each of the upper and lower cover plates are the same diameter.
As best illustrated in
When a force is applied to the lower annular face 247 of the central portion 221 of the lower cover plate 215, the tapered portion 225 is forced upwardly and is caused to deform outwardly against the vane plate 215.
Loading the impeller assembly from both sides using the upper and lower cover plates 212, 214, further increases the pressure applied between the components of the impeller assembly and substantially eliminates freeplay between individual components.
The impeller assembly 110, 210 of the second and third embodiments is assembled in a similar manner to the impeller assembly 10 of the first embodiment of the invention. Lower cover plate, vane plate and upper cover plate are placed on the drive shaft in sequence, such that lower cover plate sits against step 30. The spacer is then placed on the shaft and, if the pump is a multi-stage model, successive impeller assemblies and spacers are mounted on the shaft. Nut 32 is then tightened onto the shaft against the upper face of the upper cover plate, or against a spacer. The impeller plates are tightly pressed together as the nut 32 is tightened and the tapered portion of the upper cover plate and/or lower cover plate is forced to deform, thereby forming an assembly of impellers.
It will be appreciated that the impeller assembly of the invention is easy and relatively quick to assemble, and disassemble when required. Because each of the impeller components is individually keyed to the drive shaft, mechanical fastening of individual components to each other is no longer required and the product is made inherently more reliable. Additionally, the load of the entire impeller assembly is not borne by one plate and thus the drive feature of the impeller is under less stress, while at the same time, the impeller components are clamped together in a substantially fluid tight relationship.
It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.
Number | Date | Country | Kind |
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PQ7635 | May 2000 | AU | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCTAU01/00569 | 5/18/2001 | WO | 00 | 11/20/2002 |
Publishing Document | Publishing Date | Country | Kind |
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WO0190582 | 11/29/2001 | WO | A |
Number | Name | Date | Kind |
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1919970 | Woods | Feb 1933 | A |
6033183 | Genster | Mar 2000 | A |
Number | Date | Country |
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2260788 | Apr 1993 | GB |
Number | Date | Country | |
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20030138323 A1 | Jul 2003 | US |